Okay, I’m not quite sure how exactly you’re supposed to calculate it, but since I designed our house myself, I was able to simply click on the exterior surfaces, with the windows already excluded. That gives me 385 sqm. I also didn’t take the reveals into account. Considering that it’s now the year 2023 and we’re still building in the Stuttgart metropolitan area, you could almost see our 4,000€ as a bargain :p. That’s gallows humor...